Lubricating oils produced using wax isomerate oils and/or hydrocarbon synthesis liquid products as either the base oil or an additive component, must meet strict performance guidelines in terms of color, daylight stability, oxygenates content, engine performance test results, foaming tendency and thermal stability. The use of wax isomerate oils and/or hydrocarbon synthesis liquid products as base oils per se or as additive components of formulate lube or specialty oils (e.g. transmission fluids, refrigerator oils, electrical oils etc.) has associated with such use the necessity of overcoming and/or otherwise mitigating or removing certain negative characteristics of said oils which hamper or otherwise impede the use of such oils in such service. These oils, in the course of manufacture, and/or during shipment or storage, pick up significant quantities of oxygenates which are detrimental.
It has long been known that the presence of oxygenates in oil base stocks is to be avoided. The literature describes various methods for effecting this desired goal.
U.S. Pat. No. 3,529,944 teaches that a hydrocarbon oil can have its oxidation performance improved by the steps of adding an oxidation promoter to the oil to produce oxidation products, then filtering the oil through a solid, particulate, adsorbent media to remove the impurities. Suitable adsorbents include in general natural or synthetic clays, fuller's earth, attapulgite, silica gel and adsorbent catalyst.
U.S. Pat. No. 3,684,684 teaches the production of lube oils stable to ultra-violet light and having improved color and viscosity index by severe hydrogenation, dewaxing and clay contacting lubricating oil fractions. Clay contacting is effected using as the adsorbent agent fuller's earth, attapulgite clay, porocel clay, bauxite, silica or mixtures thereof.
U.S. Pat. No. 3,671,423 improves the light and air stability of hydrocracked high boiling fractions by percolating the oil fraction through silica-alumina gels containing a Y-type molecular sieve.
U.S. Pat. No. 4,561,967 teaches a method of stabilizing lube oil by contacting the oil with an intermediate pore size zeolite having a silica to alumina ratio of greater than about 200:1 in the hydrogen form and wherein the zeolite does not contain any hydrogenation component, the contacting being performed in the absence of hydrogen, at a pressure of less than 13 bar, a temperature of between about 260.degree. to 610.degree. C. and a LHSV of 0.5 to 200.
Despite these teachings, it would be a benefit if a low cost, low energy, repeatable process could be found for improving the color, daylight stability, oxygenates content, thermal stability, foaming characteristics and engine performance test results of wax isomerate oils and/or hydrocarbon synthesis liquid products used as base oils or additives in the production of lubricating oils, transformer fluids, refrigerator or insulating oils or other speciality oil products.